The present invention relates to the synthesis of a novel acidic fluorine-containing poly(siloxane amideimide)-silica hybrid.
Due to its excellent dielectric and mechanical properties at a high temperature and excellent thermo-oxidation stability at 180xcx9c220xc2x0 C. a poly(amideimide) meets the basic application conditions, such as high temperature resistance and insulation property, required by wires and cables. U.S. Pat. No. 5,932,351 discloses a poly(amideimide) having a good mechanical strength at a high temperature, which can be used as a thermo-resistant adhesive. Furthermore, U.S. Pat. No. 5,939,520 discloses a gas mixture separation technique by using a poly(amideimide). However, the applications of a poly(amideimide) are limited because the poly(amideimide) has a relatively high water absorbency (xcx9c4 wt %) and thermal expansion (xcx9c5xc3x9710xe2x88x925 Kxe2x88x921).
In order to improve the properties of the poly(amideimide), the present invention uses a sol-gel process to synthesize an acidic fluorine-containing poly(siloxane amideimide) silica hybrid, which is an organc-inorganic material. An organic-inorganic hybrid synthesized according to the present invention has the following structure: 
wherein
R1 is an organic tetravalent residue from 
and R1 contains a fluoro substituent;
R2 is an organic tetravalent residue from 
and R2 contains a fluoro substituent;
R3 is 
xe2x80x83wherein Rxe2x80x21, Rxe2x80x22, Rxe2x80x23 and Rxe2x80x24 are C1-C4 alkyl or phenyl, Rxe2x80x25 and Rxe2x80x26 are C1-C6 alkylene or phenylene, and n=1xcx9c10;
Rxe2x80x31 is C1-C4 alkylene or phenylene; and
Rxe2x80x32 is C1-C4 alkyl or phenyl.
Preferably, R1 is 
Preferably, R2 is from 
Preferably, Rxe2x80x21Rxe2x80x22Rxe2x80x23 and Rxe2x80x24 are methyl, Rxe2x80x25 and Rxe2x80x26 are propylene group, and n=1.
Preferably, Rxe2x80x31 is a propylene group, and Rxe2x80x32 is methyl.
The hybrid of the present invention has a stable bonding between the organic poly(amideimide) and the inorganic silica, while the inorganic silica is uniformly distributed in the organic polymer, thereby improving the mechanical properties, the chemical resistance, and the dimensional and thermal stabilities of the material. This type of organic-inorganic hybrid compound exhibits excellent complementary properties, and can effectively enhance the transparency and wear resistance of the material. The incorporation of the inorganic material is helpful in reducing the permeation activation energy of a specific gas, so that the gas selectivity becomes higher (i.e. selective permeation of a specific gas component in a multi-component gas mixture), and thus increases the gas separation efficiency.
On the other hand, the backbone of the poly(amideimide) can be introduced with functional or active groups, e.g. siloxane, fluoro-containing hydroxy, etc., to broaden the application scope of the poly(amideimide). The direct attachment of a fluoro-containing side chain (e.g. trifluoromethyl, CF3) to the backbone of poly(amideimide) can break the regularity of the molecular chain and reduce the melting point of the polymer, such that the material also possesses a good solubility, a good refractive index, a low water absorbency, a low thermal expansion, and a low dielectric constant value, while maintaining its thermal stability.
The introduction of a soft siloxane monomer in the poly(amideimide) structure can effectively increase the gas permeability and enable the poly(amideimide) exhibiting a lower water absorbency and surface energy, thereby increasing the adhesion and toughness of a poly(amideimide) membrane. While exposing to air, a protective layer will be formed on the poly(siloxane amideimide), which is advantageous in the application of this material as a micro-electronic insulation material. Furthermore, the hybrid of the present invention contains an acidic hydroxyl group (xe2x80x94OH), which can adsorb a basic gas, which is particularly advantageous to the separation of an acid/basic gas mixture.
Various successful modification techniques of the acidic fluorine-containing poly(siloxane amideimide)-silica hybrid of the present invention have greatly improved the properties and the potential in many applications of the poly(amideimide). Furthermore, additional reactants may be used to react with the acidic fluorine-containing poly(siloxane amideimide)-silica hybrid of the present invention, creating a series of organic-inorganic hybrid derivatives. Therefore, the hybrid material according to the present invention is versatile in use, and can be easily extended to other applications.